dot1q VLANs on switch of 871

[tato386]

I am trying to duplicate a VLAN setup that I have used successfully on 1700 routers on a 871 router. I purchased the Adv IP Services version of the 871 (no wireless) which is supposed to be able to do 4 dot1q VLANs. However I am realizing since the Fa0-3 interfaces on this little guy are not L3 interfaces I can't use my tried and true setup. I can't find much on how to do this other than the fact that it seems I am going to have to use bridging and BVI interfaces. What are BVI interfaces? Can they help me create something like I am showing below? If so, can anybody point me to some examples?

Thanks,

Diego

interface FastEthernet0

ip address 10.1.1.1 255.255.255.0

!

interface FastEthernet0.2

encapsulation dot1Q 2

ip address 10.1.2.1 255.255.255.0

!

interface FastEthernet0.3

encapsulation dot1Q 3

ip address 10.1.3.1 255.255.255.0

!

[tato386]

I am using the 871 as the DHCP server. However, it seems like there should be other factors at play here. What affect would the port mode (access, trunk) have on the DHCP? What about if the device is VLAN aware or not? Can you recomend a good document that explains the different switchport modes in detail?

Thanks,

Diego

[Edison Ortiz · Accepted solution]

By default, switchports are set for dynamic trunking.

If you connect a workstation, it will negotiate to access mode.

If you connect another switch with the same characteristics, the switchport will trunk.

As I stated before, if you connect a workstation to a switchport and the mode is to set to an access vlan #,

it will send a dhcp-request packet on that Vlan.

A DHCP server listening on that Vlan will reply with an IP address, if available.

If the DHCP server resides in another Vlan, you need to configure ip helper-address on the Layer3 gateway from that Vlan pointing to the remote DHCP server.

The DHCP server scope will need to have the default gateway information under the scope and this needs to match from the Layer3 gateway above.

As for the switchport mode query, this document provides some information:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_35_se/command/reference/cli3.html#wp1948171

[tato386]

Thank you sir, seems like I am well on my way to getting this all straightend out.

Rgds,

Diego